This invention relates to improvements in a rotary armature having a shrink ring type commutator.
A conventional rotary armature of the type referred to has comprised an armature core with an armature coil fitted onto a rotary shaft, an armature clamp shrink-fitted onto the rotary shaft to keep the armature core in place on the rotary shaft, and a shrink ring type commutator firmly fitted onto the rotary shaft with a prearranged space between the same and the armature clamp. The shrink ring type commutator has included a plurality of commutator segments and alternating mica pieces disposed around the rotary shaft to form an annulus coaxial with the latter, a pair of insulating shrink rings coaxial with the rotary shaft and fitted in axially aligned opposite relationship into the annulus through axially opposite surfaces thereof, and a commutator spider shrink-fitted onto the rotary shaft and onto which the shrink ring located on the side toward the armature core is fixed, and also onto which is fitted a commutator clamp onto which the other shrink ring is fitted. A plurality of ventilating holes have extended through the commutator spider, the armature core and the clamp and connected to each other to form an axial ventilation system.
In conventional rotary armatures such as described above the commutator has been fitted onto the rotary shaft through the commutator clamp and spider while, in order to support the armature core and coil, the armature clamp has been fitted onto the rotary shaft separately from the commutator. Also, in order to more and more precisely design and construct the commutator spider, clamp segments and the associated components with greater precision as required lately, they have been subjected to severe limitations as to dimensions thereof. This has resulted in an insufficient area of the ventilation passages required for cooling.
Accordingly it is an object of the present invention to provide a rotary armature including a new and improved shrink ring type commutator providing a sufficient area of the ventilation passages required for cooling in order to improve the cooling effect.